1. Field of the Invention
This invention relates to electromagnetic radiation sensors. More specifically, this invention relates to sensors disposed to detect concentrated radiation from high-energy sources.
While the present invention is described herein with reference to a particular embodiment, it is understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional embodiments within the scope thereof.
2. Description of the Related Art
Many sensitive electronic instruments are vulnerable to damage from exposure to electromagnetic radiation of sufficient intensity. Radiation from high energy lasers, for example, is often sufficient to cause permanent damage to electronic components. Many radiation hardening techniques endeavor to address this threat by detecting high energy radiation levels and activating responsive systems.
Unfortunately, certain difficulties are inherent in the process of monitoring the operational environment of such sensitive instrumentation for the presence of high radiation energy levels. For example, electronic radiation sensors, such as those incorporating photodiodes, may themselves be susceptible to damage from a source of concentrated radiation.
Thermoelectric devices such as thermocouples provide more rugged potential alternatives to sensors which include only electronic components. As is well known, thermocouples include a pair of dissimilar metallic members which interface at a junction. The potential difference across the junction varies as a function of the difference in temperature between the members (e.g. several microvolts per degree Centigrade). Unfortunately, perturbations in the electrical characteristics of the operational environment may impair the accuracy of thermocouples due to the small junction voltage gradient.
In addition, the high thermal mass of thermocouples makes the junction voltage relatively unresponsive to small temperature changes between the constituent members. As is well known, the thermal mass of a thermocouple depends on the ratio between the mass and surface area thereof. Accordingly, thermocouple sensors may be expected to respond relatively slowly to changes in the intensity of incident radiation. On the other hand, thermocouples realized from thin wire are fragile and susceptible to damage when deployed in harsh environments.
Certain types of thermopiles are also potentially suitable for use as radiation detectors. Thermopiles are conventionally employed as temperature measurement devices and generally consist of a number of thermocouples connected in series. In a particular thermopile implementation, thin films of metals (e.g. bismuth or antimony) are deposited on plastic substrates. Again, however, this type of thermopile design is fragile and susceptible to damage from excessive heat.
Accordingly, a need exists in the art for a relatively durable, lightweight radiation detector capable of withstanding exposure to intense radiation.